I'm installing a 20 amp outlet across my garage and I'm pulling 3-12 gauge
conductors. I have one square 4 inch box on each side of the garage and a
1/2" pulling elbow in the middle of the 40 foot run---so that the wire is
not being pulled through more than 270 degrees plus the box kick.

Do I pull the wires from the pulling elbow by first, pulling the wires
through one box and completely out the elbow, then running the fish tape
though the other box and pulling the wire through the elbow to the box?

Or, do I just pull the wires from one box to the other directly through the
elbow?

I tried the first option and I suspect I stripped some of the insulation off
of the wires because the hard, clear plastic sheath surrounding the
insulation was scraped up.

Any tips on pulling wire would be greatly appreciated.

thanks in advance

Ron